The goal of this application is to describe a rigorous training program for developing the applicant into a nurse scientist with a sustainable trajectory of research. The training program will provide a solid foundation of research experiences under the mentorship of established scientists in a research-intensive academic environment. The long-term objectives of this program of scholarship are to advance clinical practice by developing a physical activity intervention that promotes physical and cognitive health and prevents or minimizes disability in 'at risk' populations such as those with multiple sclerosis (MS). The purpose of the proposed study is to determine the feasibility and effects of a physical activity program on measures of clinical cognitive functioning and neurocognitive functioning in everyday life in ambulatory persons with MS experiencing cognitive problems. The specific aims of this project are to determine the feasibility of delivering the small group, moderate-intensity Physically Active Lifestyle in MS (PALMS) intervention program for persons with MS over a 6-month time period, and to explore the effects of the PALMS intervention on measures of clinical cognitive functioning, neurocognitive functioning in everyday life, exercise self-efficacy, physica activity, depressive symptoms, and fatigue. This feasibility study employs a randomized clinical trial design conducted in a community setting with a sample of 30 ambulatory adults with MS who will be recruited from the community through the applicant's long-term relationships with the National Multiple Sclerosis Society and a local MS clinic. Baseline, 3-month and 6-month (post-intervention) data collection includes neuropsychological tests of clinical cognitive functioning, performance measure of neurocognitive functioning in everyday life, exercise self-efficacy, self-reported and objective physical activity, depressive symptoms, and fatigue. Participants randomized to the intervention group will meet twice a week with the applicant and up to 4 other participants for 50 minutes of supervised aerobic physical activity. Each participant will undergo an exercise assessment and have an individualized program of exercise based on the assessment. The supervised program will consist of a ten-minute warm-up, 30 minutes of aerobic exercise (walking on a treadmill, riding a stationary bike, or using an elliptical trainer) and a ten-minute cool down with stretching. Participants will wear a heart rate monitor to assess and monitor level of exercise intensity. Participants will be encouraged to exercise on their own at least three additional days a week and to document their physical activity in a log, which will be reviewed weekly. Participants randomized to the attention-control group will be offered six months access to twice weekly, 50-minute long relaxation and stretching classes led by a trained facilitator in a community setting. Data analyses will consist of a mixed effects analysis of variance to determine intervention effects on cognitive function and other outcome variables.